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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package net.sf.saxon.functions;

import net.sf.saxon.Configuration;
import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.FunctionCall;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.parser.ContextItemStaticInfo;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.ZeroOrOne;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ConversionResult;
import net.sf.saxon.type.Converter;
import net.sf.saxon.type.ValidationException;
import net.sf.saxon.type.ValidationFailure;
import net.sf.saxon.value.*;

/**
 * Implements the XPath fn:number() function when called with one argument.
 * Note: this function accepts the value "+INF" whether or not XSD 1.1 is enabled.
 */

public class Number_1 extends ScalarSystemFunction {

    @Override
    public AtomicValue evaluate(Item arg, XPathContext context) throws XPathException {
        return toNumber((AtomicValue)arg);
    }

    @Override
    public ZeroOrOne resultWhenEmpty() {
        return new ZeroOrOne(DoubleValue.NaN);
    }

    /**
     * Simplify and validate.
     * This is a pure function so it can be simplified in advance if the arguments are known
     *
     * @param env
     */

    /*@NotNull*/
//    public Expression simplify(StaticContext env) throws XPathException {
//        useContextItemAsDefault();
//        getArg(0).setFlattened(true);
//        simplifyChildren(env);
//        return this;
//    }

    /**
     * Type-check a calling expression.
     */

    /*@NotNull*/
    public Expression typeCheckCaller(FunctionCall caller, ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) {
        if (caller.getArg(0).isCallOn(Number_1.class)) {
            // happens through repeated rewriting
            caller.setArg(0, ((FunctionCall)caller.getArg(0)).getArg(0));
        }
        return caller;
    }

    /**
     * The actual implementation logic
     * @param arg0 the atomic value to be converted
     * @return the result of the conversion
     */

    public static DoubleValue toNumber(AtomicValue arg0) throws XPathException {
        try {
            if (arg0 instanceof BooleanValue) {
                return (DoubleValue) Converter.BOOLEAN_TO_DOUBLE.convert(arg0).asAtomic();
            } else if (arg0 instanceof NumericValue) {
                return (DoubleValue) Converter.NUMERIC_TO_DOUBLE.convert(arg0).asAtomic();
            } else if (arg0 instanceof StringValue && !(arg0 instanceof AnyURIValue)) {
                // Always use the XSD 1.1 rules, which permit "+INF"
                ConversionResult cr = StringToDouble11.getInstance().convert(arg0);
                if (cr instanceof ValidationFailure) {
                    return DoubleValue.NaN;
                } else {
                    return (DoubleValue) cr;
                }
            } else {
                return DoubleValue.NaN;
            }
        } catch (ValidationException e) {
            return DoubleValue.NaN;  // should not happen
        }
    }

    /**
     * Static method to perform the same conversion as the number() function. This is different from the
     * convert(Type.DOUBLE) in that it produces NaN rather than an error for non-numeric operands.
     *
     * @param value  the value to be converted
     * @param config the Saxon configuration
     * @return the result of the conversion
     */

    public static DoubleValue convert(AtomicValue value, Configuration config) {
        try {
            if (value == null) {
                return DoubleValue.NaN;
            }
            if (value instanceof BooleanValue) {
                return new DoubleValue(((BooleanValue) value).getBooleanValue() ? 1.0e0 : 0.0e0);
            }
            if (value instanceof DoubleValue) {
                return (DoubleValue) value;
            }
            if (value instanceof NumericValue) {
                return new DoubleValue(((NumericValue) value).getDoubleValue());
            }
            if (value instanceof StringValue && !(value instanceof AnyURIValue)) {
                double d = config.getConversionRules().getStringToDoubleConverter().stringToNumber(value.getStringValueCS());
                return new DoubleValue(d);
            }
            return DoubleValue.NaN;
        } catch (NumberFormatException e) {
            return DoubleValue.NaN;
        }
    }

    /**
     * Evaluate the expression
     *
     * @param context   the dynamic evaluation context
     * @param arguments the values of the arguments, supplied as Sequences
     * @return the result of the evaluation, in the form of a Sequence
     * @throws net.sf.saxon.trans.XPathException
     *          if a dynamic error occurs during the evaluation of the expression
     */
//    public DoubleValue call(XPathContext context, Sequence[] arguments) throws XPathException {
//        AtomicValue in;
//        if (arguments.length == 0) {
//            Item c = context.getContextItem();
//            if (c == null) {
//                throw new XPathException("Context item for number() is absent");
//            }
//            if (c instanceof AtomicValue) {
//                in = (AtomicValue) c;
//            } else if (c instanceof NodeInfo) {
//                AtomicSequence as = ((NodeInfo) c).atomize();
//                if (as.getLength() == 0) {
//                    return DoubleValue.NaN;
//                } else if (as.getLength() == 1) {
//                    in = as.head();
//                } else {
//                    throw new XPathException("Atomization of context item for number() is a sequence containing more than one item", "XPTY0004");
//                }
//            } else {
//                throw new XPathException("Context item for number() cannot be atomized", "XPTY0004");
//            }
//        } else {
//            in = (AtomicValue) arguments[0].head();
//            if (in == null) {
//                return DoubleValue.NaN;
//            }
//        }
//        return convert(in, context.getConfiguration());
//    }

}